The Waikato District Health Board is warning people to continue not to collect or eat shellfish from the Bay of Plenty and Coromandel coastlines.
The board says continuing weekly testing has confirmed that toxic shellfish have been found from Tairua on eastern Coromandel through to the mouth of the Whakatane iver in the eastern Bay of Plenty.
The warning affects all bivalve shellfish including mussels, pipi, tuatua, cockles, oysters, scallops and kina.
Medical Officer of Health Phil Shoemack says two people have been admitted to hospital, with at least another four being treated at emergency departments.
He says symptoms include numbness and tingling around the mouth, as well as more severe problems such as muscle weakness and breathing problems.
Dr Shoemack says anyone with such symptoms should seek medical attention.